MCA : Practice Questions and Answers

There are three main types of services offered by the SS7 network. They are the Touchstar, 800 services, and alternate billing services.

First generation wireless systems provide analog speech and inefficient, low rate, data transmission between the base station and mobile user.

Various proposed standards such as the GSM, US digital cellular (USDC), and Pacific Digital Cellular (PDC) have adopted digital TDMA for high capacity. IS-95 does not use TDMA.

Radio capacity is a parameter which measures spectrum efficiency of a wireless system. This parameter is determined by the required carrier to interference ratio and the channel bandwidth.

The type of multiple access technique used is an important factor in determining the spectral efficiency of the system. It strongly influences the choice of speech codec.

DCT (discrete cosine transform) is one of the most attractive and frequently used transforms for speech coding. Fast algorithms developed for computing the DCT in a computationally efficient manner are used.

Constraint length determines the number of input data bits that the current output is dependent upon. The constraint length determines how powerful and complex the code is.

Block codes are linear, systematic and cyclic in nature. Encoding and decoding techniques make use of mathematical constructs known as finite fields.

Space diversity reception methods can be classified into four categories. They are selection diversity, feedback diversity, maximal ratio combining and equal gain diversity.

The structure of lattice equalizer is more complicated than a linear transversal equalizer. But, numerical stability and faster convergence are two advantage of laatic equalizer. Also, its unique structure allows dynamic assignment of the most effective length of lattice equalizer.

Equalization, diversity and channel coding are the three techniques which are used to improve received signal quality and link performance over small scale times and distance. But, the approach, cost, complexity and effectiveness varies in wireless communication system.

Outage event is specified by a specific number of bit errors occurring in a given transmission. Evaluating the probability of outage is one of the means to judge the effectiveness of the signalling scheme in a mobile radio channel.

The set of possible carrier frequencies in FH-SS is called hopset. Hopping occurs of a frequency band that includes a number of channels. Each channel is defined as a spectral region with central frequency in the hopset.

MSK has a constant envelope. It is a spectrally efficient scheme. It possesses properties such as constant envelope, spectral efficiency, good BER performance and self-synchronizing capability.

OQPSK, π/4 QPSK and BPSK are the most popular linear modulation techniques. They have very good spectral efficiency. However, FSK is an non-linear modulation technique.

Bandwidth efficiency reflects how efficiently the allocated bandwidth is utilized. It is defined as the ratio of throughput data rate per Hertz in a given bandwidth. It describes the ability of a modulation scheme to accommodate data within a limited bandwidth.

Various techniques such as slope detection, zero crossing detection, phase locked discrimination and quadrature detection are used to demodulate FM. Product detector is used for demodulating AM signals.

Three principle shape factors are angular spread, angular constriction, and azimuthal direction of maximum fading. They are exactly related to the average rate at which a received signal fades.

The level crossing rate (LCR) and average fade duration of a Rayleigh fading signal are important statistics. They are useful for designing error control codes and diversity schemes to be used in mobile communication.

Channel parameters are coherence bandwidth, rms delay spread and Doppler spread. Signal parameters are bandwidth and symbol period. Different types of fading occur depending on the relation between channel and signal parameters.